Description: A special version of the small-sliding, surface-to-surface contact formulation is automatically invoked if the slave surface is based on gasket elements, to avoid triggering unstable modes of gasket elements in certain situations. Gasket elements have very little resistance to certain shear deformation modes, which are not significant in common gasket applications; however, having multiple slave nodes per contact constraint, such as with regular surface-to-surface discretization, can trigger these modes at boundaries of an active contact region and regions with a large contact-pressure gradient. Now, the small-sliding, surface-to-surface contact formulation uses a single slave node per contact constraint if the slave surface is based on gasket elements (like the node-to-surface contact formulations), but it remains capable of providing accurate contact stress predictions despite having mismatched meshes across the contact interface.

The finite-sliding, surface-to-surface formulation always uses multiple slave nodes per contact constraint and is not recommended for contact involving gasket elements.